Production of acetaldehyde from



April l1, 1939. F. LlEsEBERG 2,153,578

` PRODUCTION OF ACBTALDEHYDE FROM GASES CNTAINING ACETYLENE Filed June 2, 1936 .sfPAATM C Fcrllch eseberlg INVENTOR HIS ATTORNEYS Patented Apr. 411, l9v39 PRODUCTION F ACETALDEHYDE FRJOM- GASES CONTAINING ACETYLENE Friedrich meseberg, Ludwigsharen-en-the-Rhme, p Germany, assigner to I. G. Farbenindustrle Aktiengesellschaft, Frankfort-on-the-Maln.

Germany Applicaudn June z, 193s, serial No. sacca In Germany June 12, 1935 2 claims. (ci. 26o-sos) The present invention relates tothe manufacture of ac'etaldehyde from gases containing acetylene.

It 'has already been proposed to prepare acetal- 5 dehyde from high percentage acetylene at ordinary or increased pressure by the addition of water with the aid of a catalytic liquid containing mercury sulphate which contains in addition to water an organic solvent for acetylene. The catalytic liquid may be led in circulation with the aid of a pump in order to keep the temperature of the catalytic liquid at the desired level by cooling or heating or in order to regulate the composition of the liquid. Since practically 100 16 per cent acetylene is employed, the acetylene may be led in circulation and there is no need to take care that as complete a conversion as possible into acetaldehyde' is effected by a single passage through the catalytic liquid. Itis more 20 diicult, however, to work up gases containing acetylene such as are obtained for example in the electric arc under conditions which are favorable industrially and economically a-nd which contain up to about 18 to 20 per cent of acetylene. These gases cannot be worked up into acetaldehyde in a cycle because the admixed inert gases which consist mainly of hydrogen become enriched and the partial pressure of acetylene in the circulating gas becomes more and more re- 430 duced. It is therefore necessary continuously to withdraw a large proportion of the gas from circulation and the acetylene contained therein is thus lost for the conversion into acetaldehyde. Since working in such' a manner is uneconomical 35 and industrially valueless, it is necessary to convert the gas mixture Vcontaining acetylene as completely as possible into acetaidehyde by a single passage of the gasthrough the catalytic liquid. It is only in this way that gases contain- 40 ing only asmall percentage of acetylene can be worked up in an advantageous manner economically Without waste of acetylene, the latter being of decisive importance as regards the possibility of using the process industrlally. 45 In order to obtain this result it has already been proposed to convert the acetylene present in gas mixtures containing acetylene into acetaldehydeI in counter-current inV towers provided with filler bodies by means of suitable catalytic 50 liquids which for example may contain iron salts in addition to mercury salts in sulphuric acid solution. 'I'he catalytic liquid must be withdrawn at the lower end of the reaction tower by means of a pump insensitive to hot sulphuric acid and 56 forced into the top of the tower in counter-current to the ascending current of gas. Such a method of working necessitates special expensive materials for the pumps and also a continuous expenditure of power for Vleading the catalytic liquid in circulation. The technical drawbacks which arise in the circulation of hot su1phuricacid by means of a pump are thus increased by the cost of the expenditure of power. Furthermore, when working in counter-current, the reaction tower cannot be loaded beyond a. certain l0 limit because otherwise the catalytic liquid flowing in counter-current to the current of gas be comes dammed up and the washing action of the liquid distributed inthe tower and'consequently also the desired reaction suffers. Thus the maxi- 15 mum throughput f or a given tower space which would otherwise be permitted by the reactivity of the catalytic liquid cannot be attained but 'the damming action places a limit on the result aimed at. It is therefore necessary to construct 20 larger or more numerous towers for working up `a given amount of acetylene. 'I'his means a considerable injurious en'ect on the possibility of employing gases containing acetylene derived from. electric arc treatments instead of high percentage 26 acetylene for working up into acetaldehyde.

I have now found that the acetylene in gases i containing acetylene such as are obtained by thermal methods. in particular in the electric arc, can be advantageously converted into acetaldehyde by leading the gas to be treated in the same direction as the catalytic liquid and leading the latter in a cycle at the same time. The circulation of the catalytic liquid is preferably carried out so that a multiple of the amount of liquid present in the reaction lvessel is circulated Der hour. This can be effected in a particularly favorable manner when `an apparatus is .used such as is shown diagrammatically in the accompanying drawing; the invention is not, however, restricted to the use of the particular ex' ample of apparatus shown.

Referring to the drawing, the gas mixture containing acetylene flows into the lower part of the tower at A. The catalytic liquid which is present therein as well as in the central part of the tower B (which may be filled with filler bodies) is car. ried up by the current of gasin the form 'of a foam and collects in the upper part of the tower C, from which it flows back to the lower part A again through an overflow pipe. The rapidity of the circulation movement of the catalytic liquid thus depends merely on the smaller specic 1 gravity by reason of the partial formation of foam in the tower and on the amount of gas mixture contamina acetylene introduced um the tower. Apumpis thereioreunn 4andalltlie dimcultiesencmmtered in pumping hot acids are thus .obviated Similarly a continuous expenditure oi,

ing acetylene into acetaldehyde, the procedure nmay be as' follows: A solution containing free sulphuric acid and ferrie sulphate is charged in an amount adapted to the size of the reaction tower into the tower at E. By blowing in steam or by indirect heating of the tower, the solution is heated to about 90 C. Mercury is charged into the portion D of the tower after the said temperature has been reached and then the gas mixture-containing acetylene is blown through 'the tube F. The catalytic solution is carried up to C, ows into D, becomes saturated with mercury compounds and ows back to A in a cycle. The mercury compounds which have been carried along are partly used up in the tower; 'the solution ows again into D, is again saturated with mercury compounds and the cycle commenoes again. By this arrangement the amount or mercury necessary for the addition of water to the acetylene is always available. The residual gas together with the aldehyde formed ows through the part C of the tower and leaves through the pipe H after which it is freed fromN aldehyde in an attached condenser and Washing tower (not shown). In this manner it is possible to obtain high throughputs and to adapt the necessary amount of catalytic liquid to the gas throughput of the tower because the amount or liquid circulated per hour is always dependent on the @as throughput. With the high throughputs obtained, o. practically complete conversion or the acetylene into acetaldehyde is obtained. In the known counter-current processes, it was only possible to work up a gos mixture coutaining 3 per cent of acetylene. According to this invention, on the contrary, cases which cou' tain up to about 18 to 2o per cent oi acetylene may be converted.

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The mercury compounds necessary for and partly 'used up by the reaction must be ireshly formed again by the reaction of metallic merculo` with ferrie salts. The ferrous salts thus formed must be oxidized again. The regeneration ci the catalytic solution may be interposed in theoycle or carried out separately therefrom.

` casacca The throughputs may be increased even more by carrying out the reaction under increased pressure.

Example A catalytic solution containing 50 grams of -i'ree sulphuric acid and 35 grams of iron in the form of ferrous `and ferric sulphate per litre is 'introduced into a tower such as is shown in the drawing. The catalytic solution is circulated and brought into contact with metallic mercury at a suitable place. The solution is thus saturated with mercury compounds of the mercurous and mercurio stages by the reaction of the metallic mercury with the ferrie sulphate. A gas mixture containing 18 yper cent by volume of acetylene is blown into the said catalytic solution with the addition o! an amount ci steam which correspends to the amount of water necessary for the addition of water to the acetylene and for the maintenance of the concentration oi the catalytic solution. The waste oas in the part C of the tower is under an excess pressure of 0.5 atmosphere. The gas and the catalytic liquid ow in the same direction. The ons mixture containing acetylene is converted by a single passage through the catalytic solution to the extent of 97.8 per cent so that in the waste gas there can only be detected 0.4 percent by volume of acetylene in addition to acetaldeliyde and accompanying gases. 9d per cent ci the amount of actylene introduced are converted into acetaldehyde, about 2 per cent into crotonaldehyde and another 1.8 per cent into acetic acid.

'What l cl is:

l. in the .production of acetaldehyde from gases containing upto about 2o per cent of acetylene by means or an acid solution containing mercury compounds the step which comprises leading @as to be treated through the reaction vessel in the same direction as the catalytic liq uid, withdrawn@ the latter-*from the upper part or the reaction Vessel, saturating it with mermuy compounds and returning it to the lower part ci' the reaction vessel.

2. in the process according to claim l the step which comprises circulating the catalytic liquid so that a multiple ol the amount of liquid pres- @ont in the reaction vessel is circulated per hour.

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